The investigation of in vitro colistin activity, which is one of the last choice agents, against pan-antibiotic resistant pseudomonas aeruginosa and stenotrophomonas maltophilia.

Multiple drug resistant bacteria is bearing high risk particularly for hospitalized patients who are with worse clinic conditions. Inappropriate antibiotic management and inadequate execution of standard infection control measurements have yielded rapid dissemination of these resistant phenotypes and emerged as a serious therapeutic problem in many countries and as well Turkey. The clinic importance of colistin (polymixin-E)) which is a polypeptide antibiotic has recently been increasing due to development of multiple drug resistance phenotypes among gram negative bacteria. However, there is limited data about the activity of colistin for multiple drug resistant bacteria in our country. In this study, colistin susceptibility was investigated with Etset (AB Biodisk) method for 57 Pseudomonas aeruginosa and 10 Stenotrophomonas maltophilia which were determined as pan-antibiotic resistant in disk difussion test, performed against to Clinic Laboratory Standards Institute (CLSI) suggested antibiotics, isolated in Firat University Medical Faculty Microbiology and Clinic Microbiology Laboratory between January 2004 and February 2007. Colistin activity against to P. aeruginosa and S. maltophilia strains were found as 57.1% and 40%, respectively. MIC50 ve MIC90 values of colistin for P. aeruginosa and S. maltophilia were 2?g/ml and 16 ?g/ml; 4 ?g/ml and 256 ?g/ml, orderly. Regarding to our results, we determined that colistin was moderately active against to studied P. aeruginosa and for S. maltophilia strains. Our resistance rates were regarded as higher when considered with the findings in the scientific literature. The main reason of these low susceptibility rates obtained was considered as the multiple resistance gene accomodation of the studied pan-antibiotic resistant starins. When concerning with the possible side effects may emerge, it will be benefit to perform in vitro susceptibility test before administration of colistin.